It is common practice in cosmetics or dermatology to use compositions consisting of a water-in-oil (W/O) emulsion comprising an aqueous phase dispersed in an oily phase. These emulsions can constitute creams, a cream being, in the fields under consideration, malleable and deformable products, as opposed to solid compositions. W/O emulsions comprise an oily continuous phase and thus make it possible to form at the surface of the skin a lipid film that prevents transepidermal water loss and protects the skin against external attack. These emulsions are particularly suitable for protecting and nourishing the skin, and in particular for treating dry skin. In addition, the lipid film formed at the surface of the skin may also increase the remanence of sunscreens. These emulsions also have the advantage of allowing the protection and transport of oxidation-sensitive hydrophilic active materials.
However, W/O emulsions have the drawback of giving a relatively greasy feel when applied to the skin, due to the fact that the oily phase is the external phase. Thus, these emulsions are generally used for dry skin, since they are too greasy to be used for greasy skin. Furthermore, W/O emulsions give no sensation of freshness and are generally too rich in oils to be used during summer or in hot countries.
Moreover, W/O emulsions have stability problems, especially when there is a large amount of aqueous phase: the drops of aqueous phase have a tendency to aggregate and to form lumps that are visible under a microscope. This aggregation is harmful to the stability of the emulsions; firstly, it promotes creaming or sedimentation of the fluid systems, and secondly the coalescence of the drops leads to the appearance of water regions, i.e. drops of aqueous phase larger than 50 microns. To stabilize these emulsions, it is often necessary to use a large proportion of emulsifiers and/or to introduce a certain amount of consistency factors, such as waxes. However, these consistency factors contribute towards accentuating the cosmetic defects (sticky and greasy effect) of the W/O emulsions, resulting in the production of compositions that are often heavy. Moreover, in the presence of these consistency factors, it is difficult to obtain fluid emulsions because these factors thicken the emulsions. In addition, if the amount of emulsifier in these emulsions is increased greatly to overcome their instability, the emulsions obtained may prove to be irritant towards certain skin types, especially sensitive skin.
Furthermore, for W/O compositions intended for removing makeup, the presence of a large amount of waxes reduces the properties of the compositions, especially of those intended for removing makeup from the skin, since the presence of waxes makes it difficult to remove the makeup remover when it is wiped or when it is rinsed (poor rinsability).
There is thus still a need for a W/O emulsion, which may especially be in cream form or in solid form, which does not have the drawbacks encountered with those known hitherto, in particular for an emulsion with a light and fresh feel, and which has good stability, even in the absence of the usual consistency factors of the oily phase, and especially even in the absence of waxes, even if it is desired to obtain a composition in solid form.